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Tsirkin" , Jason Wang , Pankaj Gupta , Michal Hocko , Oscar Salvador Subject: Re: [PATCH stable 5.10] mm/memory_hotplug: extend offline_and_remove_memory() to handle more than one memory block Message-ID: <2023061926-monoxide-pastor-fa3b@gregkh> References: <20230619065121.1720912-1-mawupeng1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230619065121.1720912-1-mawupeng1@huawei.com> X-Rspamd-Queue-Id: 78BD2C0002 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: fb6zthacqy6cx1rwnt5rx78iyr49psu5 X-HE-Tag: 1687159012-730674 X-HE-Meta: U2FsdGVkX1+cBicc7B1V4VSdfa735B86XPm9rTfwMUlN+hTli9UmDXEatnC55i5RfCMFDNWqIXDn531S2Qg5zzlbrzULm2dqigIWlMF3U/mNPoCO5dlWxVXagZqM1y+lENFuqjM3CXEN7GQz7HaiPOjbuj9JT47xIzHpPI7mxttD1/XnjaCTJQFhsFdzQKF0gQLeDv8KTKSDD8RAK3w6PenJsMmZNvU0PEoxW6uxZahSqD0MehciYDfVaWvNCL9Zqpsi2v/d521l+a786LYIlMBetRzLBjnwUpGC1TkLoQC4BE4m2s5/Pw85r2fafwePvU6oGcT+Er9hKgLkJHlebOu/dcrVq3pnF2KGElkhQ5OM9yyrHWsXhWRYnHARNSPZ6WntQJtRPeLdAowvSIqDj8kElwsn1gc9FrugKjoFo0szMml+RL/qJbTy5cuAtL4OY3LQIkmjIFd+kgcSjyHgBZKpH3I3speqbWElq9Bj7Fh+7ETNfzjUqbzbCQ84AvjeaULuDuuc6D7oHVtedjrSUXdSNCPA0DwZzMGRhvIbZdyVLPUMD9xmNgEAcwa8p2TI9f2NgbfINsEo+Lgs1AkvTQRnvM7b7YdWJC1F0zim8oRd/l5hF23dRvq342dONNxOVGgddcOsCMzl+urfxINXbY0kwNfXSSsJtMwZVs4aoGBKjEqeQWqsEfCtHOSg3puWr/HBzH20wH4gS0pOOm5rbHf0os6fyOkG+tIhx+h5Jt/uzYpwbn023dHliUGa7e3W+9wKFgOJSilLFYw5BHQizvJ4dsmA0wAhNsBESyF3MkiEsUDIdD9OKdV1SGxlWgpbhPdTNoVvgf6iztMlFWMmQSYHJPzPgwSaqj2zzJqM3r5ti94G/TvXnYBUpcfnjBXF9JCGVE8/X7osVzXnpjCkx2WAeNADxDx4uqJayv9ymYyaiUr+57g3UgrfFwW0rryzgmZ6++u7srRbcplsIYA Plw+5nmL 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jun 19, 2023 at 02:51:21PM +0800, Wupeng Ma wrote: > From: David Hildenbrand > > commit 8dc4bb58a146655eb057247d7c9d19e73928715b upstream. > > virtio-mem soon wants to use offline_and_remove_memory() memory that > exceeds a single Linux memory block (memory_block_size_bytes()). Let's > remove that restriction. > > Let's remember the old state and try to restore that if anything goes > wrong. While re-onlining can, in general, fail, it's highly unlikely to > happen (usually only when a notifier fails to allocate memory, and these > are rather rare). > > This will be used by virtio-mem to offline+remove memory ranges that are > bigger than a single memory block - for example, with a device block > size of 1 GiB (e.g., gigantic pages in the hypervisor) and a Linux memory > block size of 128MB. > > While we could compress the state into 2 bit, using 8 bit is much > easier. > > This handling is similar, but different to acpi_scan_try_to_offline(): > > a) We don't try to offline twice. I am not sure if this CONFIG_MEMCG > optimization is still relevant - it should only apply to ZONE_NORMAL > (where we have no guarantees). If relevant, we can always add it. > > b) acpi_scan_try_to_offline() simply onlines all memory in case > something goes wrong. It doesn't restore previous online type. Let's do > that, so we won't overwrite what e.g., user space configured. > > Reviewed-by: Wei Yang > Cc: "Michael S. Tsirkin" > Cc: Jason Wang > Cc: Pankaj Gupta > Cc: Michal Hocko > Cc: Oscar Salvador > Cc: Wei Yang > Cc: Andrew Morton > Signed-off-by: David Hildenbrand > Link: https://lore.kernel.org/r/20201112133815.13332-28-david@redhat.com > Signed-off-by: Michael S. Tsirkin > Acked-by: Andrew Morton > Signed-off-by: Ma Wupeng > --- > mm/memory_hotplug.c | 105 +++++++++++++++++++++++++++++++++++++------- > 1 file changed, 89 insertions(+), 16 deletions(-) > Why is this needed in 5.10.y? Looks like a new feature to me, what problem does it solve there? thanks, greg k-h